JP4995718B2 - Process for producing unsaturated aldehyde and unsaturated carboxylic acid - Google Patents

Description

  The present invention relates to a method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, specifically, propylene, isobutylene or tertiary butanol is subjected to gas phase catalytic oxidation with molecular oxygen in the presence of a catalyst, and the corresponding unsaturated aldehyde and The present invention relates to a method for producing an unsaturated carboxylic acid.

  Methods for producing propylene, isobutylene or tertiary butanol by gas phase catalytic oxidation in the presence of a catalyst to produce the corresponding unsaturated aldehyde and unsaturated carboxylic acid are widely known and used industrially. Yes. As the catalyst, for example, a catalyst made of a composite oxide containing molybdenum, bismuth and iron as essential components is used (Patent Documents 1 to 6). In this case, the reaction is carried out at a temperature of 300 to 400 ° C. using the catalyst as a fixed bed.

Although the catalyst used for such a gas phase catalytic oxidation reaction is used for a relatively long period of time, usually the activity of the catalyst decreases with time, and the reaction rate of the raw material decreases. Usually, in a fixed bed reactor, with the decrease in activity over time, a method of maintaining the reaction rate of the raw material by increasing the reaction temperature to the allowable temperature of the process is employed (Patent Document 7, Non-Patent Document). 1).
JP-A-53-19188 JP 54-66610 A JP-A-55-359 Japanese Unexamined Patent Publication No. 55-19227 JP-A-56-95135 Japanese Unexamined Patent Publication No. 60-28824 Japanese Patent Application Laid-Open No. 11-267339 Supervised by Yuichi Murakami Catalyst degradation mechanism and prevention measures, Section 17 (Technical Information Association)

  However, according to the study by the present inventors, the control of only the reaction temperature as described in Patent Document 7 and Non-Patent Document 1 has a relatively fast rate of decrease in activity, which is not necessarily from the viewpoint of industrial implementation. It is not satisfactory enough.

  Therefore, the present invention provides a method for using a catalyst for a long period of time in the gas phase catalytic oxidation of propylene, isobutylene or tertiary butanol with molecular oxygen to produce the corresponding unsaturated aldehyde and unsaturated carboxylic acid. The purpose is to provide.

  In the present invention, in the presence of a catalyst comprising a complex oxide containing molybdenum, bismuth and iron as essential components, propylene, isobutylene or tertiary butanol as raw materials are subjected to gas phase catalytic oxidation with molecular oxygen, respectively. A method for producing a corresponding unsaturated aldehyde and unsaturated carboxylic acid, wherein the starting material has a temperature range of (TA-15) ° C. to TA ° C., where TA is the boundary temperature of the activation energy of the catalyst. It is the manufacturing method of unsaturated aldehyde and unsaturated carboxylic acid characterized by performing control which changes reaction pressure so that the reaction rate of may become constant.

  In the present invention, in the presence of a catalyst comprising a composite oxide containing molybdenum, bismuth and iron as essential components, isobutylene or tertiary butanol as a raw material is subjected to gas phase catalytic oxidation with molecular oxygen, A method for producing a corresponding unsaturated aldehyde and unsaturated carboxylic acid, wherein the starting material has a temperature range of (TA-15) ° C. to TA ° C., where TA is the boundary temperature of the activation energy of the catalyst. It is a method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, characterized in that control is performed to change the molar ratio of oxygen and raw material so that the reaction rate of is constant. As the control, the reaction pressure can be further changed.

  According to the method for producing unsaturated aldehyde and unsaturated carboxylic acid of the present invention, the catalyst can be used for a substantially long period of time.

2 is a diagram showing a control method for a second reaction in Example 1. FIG. FIG. 3 is a diagram showing a method for controlling a second reaction in Example 2. FIG. 4 is a diagram showing a method for controlling a second reaction in Example 3. FIG. 4 is a diagram showing a method for controlling a second reaction in Example 4. It is a figure which shows the control method of the 2nd reaction in the comparative example 1.

  In the present invention, propylene, isobutylene or tertiary butanol (hereinafter also referred to as TBA) is subjected to gas phase catalytic oxidation with molecular oxygen to produce the corresponding unsaturated aldehyde and unsaturated carboxylic acid. A catalyst comprising a complex oxide containing bismuth and iron as essential components is used. The corresponding unsaturated aldehyde and unsaturated carboxylic acid when starting from propylene are acrolein and acrylic acid, and the corresponding unsaturated aldehyde and unsaturated carboxylic acid when starting from isobutylene or tertiary butanol are methacrolein And methacrylic acid.

  The catalyst used in the present invention is composed of a composite oxide containing molybdenum, bismuth and iron as essential components, and there are no particular limitations on components other than the essential components in the composite oxide. Such a catalyst can be obtained by a known method as described in Patent Documents 1-6.

  The catalyst used in the present invention is preferably a composite oxide having a composition represented by the following formula (1).

_{Mo a Bi b Fe c M d} X e Y f Z g Si h O i (1)
In the formula (1), Mo, Bi, Fe, Si and O each represent molybdenum, bismuth, iron, silicon and oxygen, M represents at least one element selected from the group consisting of cobalt and nickel, X represents at least one element selected from the group consisting of chromium, lead, manganese, calcium, magnesium, niobium, silver, barium, tin, tantalum and zinc, and Y represents phosphorus, boron, sulfur, selenium, tellurium, Z indicates at least one element selected from the group consisting of cerium, tungsten, antimony and titanium, and Z indicates at least one element selected from the group consisting of lithium, sodium, potassium, rubidium, cesium and thallium. a, b, c, d, e, f, g, h, and i represent the atomic ratio of each element, and when a = 12, b = 0.01-3, c = 0.01-5, d = 1 to 12, e = 0 to 8, f = 0 to 5, g = 0.001 to 2, h = 0 to 20, and i is an oxygen atom necessary for satisfying the valence of each component. It is a ratio.

  The composite oxide that is a catalyst used in the present invention may be supported on a carrier. Examples of the carrier include silica, alumina, silica-alumina, magnesia, titania, silicon carbide and the like.

  Hereafter, the suitable manufacturing method of the catalyst used in this invention is demonstrated.

  The raw material of the element constituting the catalyst (hereinafter sometimes abbreviated as catalyst raw material) is not particularly limited, but is usually an oxide, chloride, hydroxide, sulfate, nitrate, carbonate, acetate, ammonium. Salts or mixtures thereof are used. When using a chloride, it is preferable to select from chlorides that can be converted into oxides when ignited. Furthermore, it is also possible to use not only water-soluble compounds that are commonly used, but also metals and sparingly soluble compounds.

  First, a solution or dispersion (liquid A) containing at least molybdenum is prepared. That is, at least a molybdenum raw material is dissolved or dispersed in a solvent. It is preferable to use ammonium paramolybdate as the molybdenum raw material, but various raw materials such as molybdenum trioxide and molybdenum chloride can also be used. Furthermore, when manufacturing the catalyst represented by the above formula (1) in the liquid A, a part or all of the catalyst raw materials corresponding to bismuth, M component, X component, Y component, Z component, and silicon It can also be added during or after the preparation of solution A. However, it is preferable not to add an iron raw material, and it is preferable that A liquid does not contain iron.

  As a solvent for the liquid A, water, alcohol, acetone or the like can be used. Two or more mixed solvents selected from these may be used. At least water is preferably used as a solvent, and 50% by mass or more of the entire solvent is preferably water. It is also preferable to use water alone as the solvent.

  As for the mass of the solvent used when preparing A liquid, 70-270 mass parts is preferable with respect to a total of 100 mass parts of the catalyst raw material added to A liquid.

  On the other hand, a solution or dispersion (liquid B) containing at least iron is prepared. That is, at least an iron raw material is dissolved or dispersed in a solvent. Ferric nitrate is preferably used as the iron raw material, but various raw materials such as iron hydroxide and iron trioxide can also be used. Furthermore, when manufacturing the catalyst represented by the above-mentioned formula (1) in the B liquid, a part or all of the catalyst raw material corresponding to bismuth, M component, X component, Y component, Z component, and silicon It can also be added during or after the preparation of solution B. However, it is preferable not to add a molybdenum raw material, and the liquid B preferably does not contain molybdenum.

  As a solvent for the liquid B, water, alcohol, acetone, or the like can be used. Two or more mixed solvents selected from these may be used. At least water is preferably used as a solvent, and 50% by mass or more of the entire solvent is preferably water. It is also preferable to use water alone as the solvent.

  As for the mass of the solvent used when preparing B liquid, 30-230 mass parts is preferable with respect to a total of 100 mass parts of the catalyst raw material added to B liquid.

  And the solution or dispersion liquid (C liquid) which mixed A liquid and B liquid prepared as mentioned above is prepared. Furthermore, in the case where the catalyst represented by the above formula (1) is produced in the liquid C, a part or all of the catalyst raw material corresponding to bismuth, M component, X component, Y component, Z component, and silicon is added. It is also possible to add during or after the preparation of solution C. And finally, it is set as D liquid.

  The raw materials of bismuth, M component, X component, Y component, Z component, and silicon may be added so that a necessary amount of elements are contained in the finally obtained D liquid. About the catalyst raw material, the whole amount may be added to one of the A liquid, the B liquid, and the C liquid at a time, and divided into two or more, and each of the A liquid, the B liquid, and the C liquid multiple times. It may be added separately.

  By the method as described above, a solution or dispersion (liquid D) containing at least molybdenum, bismuth, and iron can be prepared using necessary catalyst raw materials. When producing a catalyst in which a composite oxide is supported on a support, the subsequent treatment may be carried out in the presence of the support in the D solution.

  Subsequently, it is preferable to hold | maintain the obtained D liquid in a 80-120 degreeC temperature range. The holding temperature is more preferably a temperature range of 90 to 110 ° C. By keeping the D liquid in this temperature range, the catalyst performance can be further improved.

  Although it does not specifically limit as holding time, The range of 1 second-30 hours is suitable, Preferably it is the range of 1 minute-20 hours, Most preferably, it is the range of 3 minutes-15 hours. If the holding time is too short, it is difficult to obtain the effect of improving the catalyst performance by holding. Even if the holding time is too long, it is difficult to obtain a further effect by holding. Although it is not clear why the catalyst performance is further improved by maintaining in this temperature range, it is considered that the catalyst performance is improved by improving the reactivity of the catalyst precursor.

  Subsequently, drying and baking are performed as necessary. As a drying method, various drying methods such as a box dryer, evaporation drying, spray drying and the like can be used. For example, in the case of a box dryer, the drying conditions are preferably 30 to 150 ° C., and in the case of a spray dryer, the inlet temperature is preferably 100 to 500 ° C. Moreover, there are no particular limitations on the firing conditions, and known firing conditions can be applied. Firing is usually performed in a temperature range of 200 to 600 ° C. for 0.5 to 10 hours. Moreover, it is preferable to perform the firing separately for salt decomposition and subsequent firing.

  Thereafter, the obtained catalyst can be molded. In addition, the method for molding the catalyst is not particularly limited, and using a general powder molding machine such as a tableting molding machine, an extrusion molding machine, a rolling granulator, a spherical shape, a ring shape, a cylindrical shape, It can be molded into any shape such as a star shape.

  Further, when molding the catalyst, conventionally known additives such as organic compounds such as polyvinyl alcohol and carboxymethyl cellulose may be further added. Further, inorganic compounds such as graphite and diatomaceous earth, and inorganic fibers such as glass fiber, ceramic fiber and carbon fiber may be added.

  The molded catalyst is heat-treated as necessary. The heat treatment conditions are not particularly limited, and known heat treatment conditions can be applied. The heat treatment is usually performed in a temperature range of 150 to 600 ° C. for 0.5 to 80 hours.

  As described above, a catalyst composed of a composite oxide containing at least molybdenum, bismuth, and iron can be obtained.

  The catalyst can also be used after diluted with an inert substance such as silica, alumina, silica-alumina, magnesia, titania, silicon carbide and the like.

  In the present invention, propylene, isobutylene or tertiary butanol as raw materials is vapor-phase catalytically oxidized with molecular oxygen in the presence of the catalyst as described above, and the corresponding unsaturated aldehyde and unsaturated carboxylic acid are produced. To do. For example, gas phase catalytic oxidation can be performed by passing a reaction gas containing a raw material and molecular oxygen through a reaction tube filled with the catalyst.

  It is economical to use air as the molecular oxygen source, but if necessary, air enriched with pure oxygen can be used. The concentration ratio (molar ratio) between the molecular oxygen in the reaction gas and the raw material is preferably in the range of 0.5 to 3: 1. The reaction gas preferably contains an inert gas for dilution. The reaction gas may contain water vapor. The concentration of the raw material in the reaction gas is preferably 1 to 10% by volume.

  The reaction pressure is preferably 20 to 300 kPa (gauge pressure; hereinafter, all pressure expressions are gauge pressures) as an average pressure of the inlet pressure and outlet pressure of the reaction tube. The reaction temperature can be selected in the range of 200 to 450 ° C. The range of 250-400 degreeC is preferable, and the range of 310-380 degreeC is more preferable.

  However, the activity of the catalyst used for such gas phase catalytic oxidation decreases with time. Causes of the decrease in activity include decomposition of the catalyst structure due to temperature (sublimation and scattering of the catalyst component, change of the crystal phase in the catalyst structure), reduction of the catalyst component by the reactant, reduction of the catalyst component by the reactant and temperature, etc. There are various theories. As a result of intensive studies, the present inventors have found that in the present catalyst system, the degradation of the catalyst structure due to temperature or the reduction of the reaction product and the catalyst component due to temperature is dominant as the cause of deterioration, leading to the present invention. It is a thing.

  That is, in the present invention, in order to maintain the reaction rate of the raw material without increasing the reaction temperature as much as possible, (TA-15) ° C. or higher and TA ° C. or lower (where TA (° C.) is the boundary temperature of the activation energy of the catalyst. ), The reaction pressure and / or the molecular oxygen / raw material molar ratio (O / R) in the reaction gas are controlled to be changed. By performing such control, decomposition due to the temperature of the catalyst structure and reduction of the reaction components and the catalyst components due to temperature are suppressed, and the catalyst usage period (catalyst life) compared to conventional control of only the reaction temperature. Is drastically improved. TA (° C.) can be obtained by the method described in Patent Document 7.

  In a gas phase catalytic reaction using a solid catalyst, it is often known that the activation energy of a target reaction has different values between a low temperature region and a high temperature region with a certain reaction temperature as a boundary. For example, JOURNAL OF CATALYSIS Vol. 41, pp. 134-139, has a different activation energy as described above in a reaction in which 1-butene is catalytically oxidized on a catalyst composed of a composite oxide containing molybdenum and bismuth. It has been reported. Such a behavior is a phenomenon observed because the rate-determining step of the reaction varies depending on the reaction temperature, and is described in detail in Kodansha Catalyst Course Volume 1 Section 4 (Catalytic Society). According to one theory, in the region where the reaction temperature is low, the reaction of the reactive molecule on the catalytic active point is the rate-limiting step, and in the region where the reaction temperature is high, the diffusion of the reactive molecule to the catalytic active point is estimated to be the rate-limiting step. Has been.

  In the presence of a catalyst composed of a composite oxide containing molybdenum, bismuth and iron as essential components, the present inventors have carried out a gas phase catalytic oxidation of isobutylene with molecular oxygen to produce methacrolein and methacrylic acid. When the activation energy was analyzed, it was confirmed that the values were different in the low and high reaction temperature regions.

  In the present invention, the boundary temperature TA (° C.) of the activation energy is obtained as follows. First, a catalyst is filled in a reaction tube equipped with a heat medium bath, and the temperature of the heat medium bath is changed within a range of 315 to 375 ° C. at intervals of 2 to 5 ° C., and the reaction rate of isobutylene at each temperature is obtained. Here, the reaction rate is obtained by the following equation.

Reaction rate of isobutylene (%) = A / B × 100
(A represents the number of moles of reacted isobutylene, and B represents the number of moles of isobutylene supplied.)
Subsequently, a reaction rate constant is obtained by the following equation.

K = (SV) × (1 / ρ) × ln [100 / (100−X)]
(K represents the reaction rate constant, SV represents the space velocity, ρ represents the packing density of the catalyst, and X represents the reaction rate (%) of the raw material.)
Subsequently, 1 / T is plotted on the horizontal axis and lnK is plotted on the vertical axis, and each data is plotted. Then, two approximate straight lines are drawn to determine the inclination. Here, 1 / T represents the reciprocal of the heat medium bath temperature (absolute temperature) of the reaction tube, and lnK represents the natural logarithm of the reaction rate constant. The approximate straight line can be obtained by a general method such as a least square method. The value obtained by multiplying the absolute value of the slope of the obtained approximate line by the gas constant is the activation energy to be calculated, and the reciprocal of the abscissa of the intersection of the two approximate lines is the boundary temperature TA (° C) of the activation energy to be calculated is there.

  When tertiary butanol is used instead of isobutylene as a raw material, tertiary butanol is rapidly decomposed into isobutylene and water in the presence of a catalyst containing molybdenum, bismuth and iron as essential components. That is, even when tertiary butanol is used as a reaction raw material, the reaction form is considered to be essentially the same as the oxidation reaction of isobutylene. Therefore, even when tertiary butanol is used as a reaction raw material, the boundary temperature of the activation energy of the reaction from isobutylene can be used as it is.

  Even when propylene is used as a raw material, the boundary temperature of the activation energy can be obtained as in the case of isobutylene.

  It is effective to control the reaction pressure to increase as the reaction proceeds. The pressure at the start of the reaction is preferably 90 to 110 kPa, and more preferably 95 to 105 kPa. The pressure at the end of the reaction is preferably 105 to 125 kPa, more preferably 110 to 120 kPa. Although the reaction pressure may be continuously increased, it is preferably increased stepwise from the viewpoint of ease of control. When increasing the reaction pressure stepwise, it is preferable to increase the reaction pressure in two or more steps. In the case of increasing in two steps, for example, it is preferable that the initial reaction pressure is 95 to 105 kPa, the reaction pressure is once set to 100 to 110 kPa during the reaction, and the reaction pressure is finally set to 110 to 120 kPa. In addition, the reaction pressure said here is an average pressure of the input pressure of a reactor, and an output pressure.

  It is effective to control the molecular oxygen / raw material molar ratio (O / R) in the reaction gas to increase as the reaction proceeds. The molar ratio (O / R) at the start of the reaction is preferably 1.8 to 2.2, more preferably 1.9 to 2.1. The molar ratio (O / R) at the end of the reaction is preferably 2.1 to 2.5, and more preferably 2.2 to 2.4. Although the molar ratio (O / R) may be continuously increased, it is preferably increased stepwise from the viewpoint of ease of control. When raising in steps, it is preferable to raise in two or more steps. In the case of increasing in two steps, for example, the initial molar ratio (O / R) is 1.95 to 2.05, and the molar ratio (O / R) is once 2.10 to 2.20 during the reaction, It is preferable that the molar ratio (O / R) is finally 2.25 to 2.35.

  The reaction pressure and the molecular oxygen / raw material molar ratio (O / R) in the reaction gas may be controlled by changing only one of them, but a great effect can be obtained by controlling both of them. It is done. When changing both, you may change simultaneously and may change alternately.

  In changing the reaction pressure and / or the molar ratio of molecular oxygen / raw material in the reaction gas, the conditions may be returned over time depending on the degree of change in the activity of the catalyst.

  The reaction pressure and / or the molecular oxygen / raw material molar ratio in the reaction gas are changed so that the reaction rate of the raw material becomes constant. Here, “the reaction rate of the raw material is constant” means that it is within a range of ± 2% from the operation management reaction rate during steady operation. The operation management response rate is a target response rate during steady operation. For example, when the reaction rate of the raw material is reduced to (reaction rate of the raw material at the start of reaction−2)%, the reaction is performed so that the reaction rate of the raw material does not exceed (reaction rate of the raw material at the start of reaction + 2)%. The pressure and / or the molecular oxygen / raw material molar ratio in the reaction gas may be changed.

  However, TBA is rapidly decomposed into isobutylene and water in the presence of a catalyst containing molybdenum, bismuth and iron as essential components as described above. Therefore, the reaction rate of TBA is calculated by assuming that TBA decomposes 100% into isobutylene and using that isobutylene as a raw material.

  In addition to the control for changing the reaction pressure and / or the molecular oxygen / raw material molar ratio (O / R) in the reaction gas, a higher effect can be obtained by controlling the reaction temperature. .

  The production method of the present invention can also be used in combination with an activation treatment as described in Patent Document 7. That is, it is also possible to activate the catalyst by keeping the catalyst at a temperature of 300 ° C. or higher and lower than 550 ° C. and contacting a gas substantially consisting of air for 1 hour or longer.

  The catalyst after the reaction under the control can be further used for ordinary gas phase catalytic oxidation, and the period of use (catalyst life) of the catalyst at that time is also improved.

The present invention will now be illustrated by examples. However, “parts” in the description means parts by mass. The reaction product was analyzed by gas chromatography. Moreover, the reaction rate of isobutylene as a raw material and the selectivity of the produced methacrolein and methacrylic acid are defined as follows.
Raw material reaction rate (%) = A / B × 100
(A represents the number of moles of the reacted raw material, and B represents the number of moles of the supplied raw material.)
Selectivity of methacrolein (%) = C / A × 100
(A represents the number of moles of reacted raw material, and C represents the number of moles of methacrolein produced.)
Methacrylic acid selectivity (%) = D / A × 100
(A represents the number of moles of the reacted raw material, and D represents the number of moles of methacrylic acid produced.)
The composition of the catalyst precursor powder other than oxygen was estimated by ICP emission analysis and atomic absorption analysis of the catalyst precursor powder dissolved in hydrochloric acid.

[Reference example]
(Manufacture of catalyst)
Next, 3000 parts of ammonium paramolybdate was dissolved in 6000 parts of water, followed by addition of 330.2 parts of antimony trioxide with stirring, and the mixture was heated to 50 ° C. to obtain Liquid A. Separately, 972.5 parts of iron (III) nitrate, 3296.8 parts of cobalt nitrate, 84.3 parts of zinc nitrate, and 110.4 parts of cesium nitrate are dissolved in 5500 parts of water, and 300 parts of water are added thereto. A solution in which 150 parts of a 60 mass% nitric acid aqueous solution and 480.8 parts of bismuth nitrate were dissolved was added, and the mixture was heated to 30 ° C. to prepare a B solution.

  Under stirring, liquid B was mixed with liquid A to obtain a slurry, which was aged at 90 ° C. for 2 hours, then heated to 103 ° C. and concentrated for 1 hour, and then a dry powder was obtained using a spray dryer. . The obtained dry powder was calcined at 300 ° C. for 4 hours to obtain a catalyst precursor powder having the following composition.

_{Mo 12 Bi 0.7 Fe 1.7 Co 8} Zn 0.2 Cs 0.4 Sb 0.8 O x
(In the formula, Mo, Bi, Fe, Co, Zn, Cs, Sb, and O represent molybdenum, bismuth, iron, cobalt, zinc, cesium, antimony, and oxygen, respectively. (Atomic ratio, x is the atomic ratio of oxygen necessary to satisfy the valence of each component)
After 3920 parts of the obtained catalyst precursor powder was well mixed with 80 parts of methylcellulose powder, 1490 parts of pure water was added, kneaded, and formed into a ring shape having an outer diameter of 5 mm, an inner diameter of 2 mm, and a height of 5 mm by extrusion molding. The molded body was heat-treated at 510 ° C. for 2 hours to obtain a catalyst.

(Determination of catalyst activation energy boundary temperature TA (° C))
2000 g of the obtained catalyst was packed into a stainless steel reaction tube having an internal diameter of 27.5 mm and a height of 4 m, which has a heat medium bath outside. Subsequently, the temperature of the heat medium bath is set to 315 under the condition that a reaction gas consisting of 5% by volume of isobutylene, 12% by volume of oxygen, 10% by volume of water vapor, and 73% by volume of nitrogen is passed through the catalyst layer with a contact time of 3.5 seconds. Gas phase catalytic oxidation of isobutylene changed at intervals of 2 to 5 ° C. in a range of ˜375 ° C. was performed, and activation energy was calculated from the reaction rate of isobutylene at each temperature. As a result, the activation energy boundary temperature TA (° C.) was 335 ° C., the activation energy at a temperature lower than the boundary temperature was 100 kJ / mol, and the activation energy at a high temperature region was 32 kJ / mol. The average reaction pressure was 98 kPa.

[Example 1]
(First reaction)
The reaction tube used in the reference example was charged with 2000 g of the catalyst obtained in the reference example. Subsequently, the temperature of the heat medium bath is set to 320 ° C., and a reaction gas composed of 5% by volume of isobutylene (reaction raw material), 9% by volume of oxygen, 10% by volume of water vapor and 76% by volume of nitrogen is contacted at a contact time of 4.5 seconds. The gas phase catalytic oxidation of isobutylene was carried out under the condition of passing through. As a result of analyzing the initial reaction product, the reaction rate of isobutylene was 95.7%, the selectivity of methacrolein was 87.9%, and the selectivity of methacrylic acid was 5.4%. The temperature of the heat medium bath at this stage is 320 ° C., the average reaction pressure is 100 kPa, and the molecular oxygen / raw material molar ratio in the reaction gas is 2.0 (initial reaction conditions).

(Second reaction)
Following the first reaction, control was performed at an operation management reaction rate of 95%. Specifically, as shown in FIG. 1, the temperature of the heat medium bath, the average reaction pressure, and the molecular oxygen / raw material molar ratio in the reaction gas were changed. The period of continuous operation was 14700 hours. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.7%, the selectivity of methacrolein was 87.8%, and the selectivity of methacrylic acid was 5.3%. The temperature of the heat medium bath at this stage is 335 ° C., the average reaction pressure is 110 kPa, and the molecular oxygen / raw material molar ratio in the reaction gas is 2.3 (reaction condition 1).

(Third reaction)
After the second reaction, the reaction was temporarily stopped and the reaction was restarted under the initial reaction conditions. As a result of analyzing the reaction product at the initial stage of the restart, the reaction rate of isobutylene was 93.5%, the selectivity of methacrolein was 87.7%, and the selectivity of methacrylic acid was 5.3%.

(4th reaction)
After the third reaction, the reaction condition is changed to reaction condition 1 until the temperature of the heat medium bath reaches 360 ° C. while controlling to increase the temperature of the heat medium bath so that the reaction rate of isobutylene becomes constant. The reaction was continued. The total duration of continuous operation was 19,200 hours. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.7%, the selectivity of methacrolein was 87.6%, and the selectivity of methacrylic acid was 5.3%.

[Example 2]
(First reaction)
The first reaction was carried out in the same manner as in Example 1.

(Second reaction)
Following the first reaction, as shown in FIG. 2, the second reaction was performed in the same manner as in Example 1 except that the temperature of the heat medium bath and the average reaction pressure were changed. The period of continuous operation was 7520 hours. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.6%, the selectivity of methacrolein was 87.9%, and the selectivity of methacrylic acid was 5.4%. The temperature of the heat medium bath at this stage is 335 ° C., the average reaction pressure is 110 kPa, and the molecular oxygen / raw material molar ratio in the reaction gas is 2.0 (reaction condition 2).

(Third reaction)
After the second reaction, the third reaction was performed in the same manner as in Example 1. As a result of analyzing the reaction product at the initial stage of the restart, the reaction rate of isobutylene was 93.4%, the selectivity of methacrolein was 87.8%, and the selectivity of methacrylic acid was 5.4%.

(4th reaction)
After the third reaction, the fourth reaction was performed in the same manner as in Example 1 except that the reaction condition was changed to the reaction condition 2, and the reaction was continued until the temperature of the heat medium bath reached 360 ° C. The total duration of continuous operation was 14400 hours. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.6%, the selectivity of methacrolein was 87.7%, and the selectivity of methacrylic acid was 5.4%.

[Example 3]
(First reaction)
The first reaction was carried out in the same manner as in Example 1.

(Second reaction)
Subsequent to the first reaction, as shown in FIG. 3, the second reaction was carried out in the same manner as in Example 1 except that the temperature of the heat medium bath and the molar ratio of molecular oxygen / raw material in the reaction gas were changed. . The period of continuous operation was 8000 hours. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.7%, the selectivity of methacrolein was 87.9%, and the selectivity of methacrylic acid was 5.4%. The temperature of the heat medium bath at this stage is 335 ° C., the average reaction pressure is 100 kPa, and the molecular oxygen / raw material molar ratio in the reaction gas is 2.3 (reaction condition 3).

(Third reaction)
After the second reaction, the third reaction was performed in the same manner as in Example 1. As a result of analyzing the reaction product at the initial stage of the restart, the reaction rate of isobutylene was 93.5%, the selectivity of methacrolein was 87.9%, and the selectivity of methacrylic acid was 5.4%.

(4th reaction)
After the third reaction, the fourth reaction was performed in the same manner as in Example 1 except that the reaction condition was changed to the reaction condition 3, and the reaction was continued until the temperature of the heat medium bath reached 360 ° C. The period of continuous operation was 15000 hours in total. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.7%, the selectivity of methacrolein was 87.7%, and the selectivity of methacrylic acid was 5.4%.

[Example 4]
Tertiary butanol (TBA) is used as a reaction raw material instead of isobutylene, and in the second reaction, as shown in FIG. 4, the temperature of the heat medium bath, the average reaction pressure, and the molecular oxygen / raw material in the reaction gas The reaction was carried out in the same manner as in Example 1 except that the molar ratio was changed. The reaction rate of TBA was calculated by assuming that TBA decomposes 100% into isobutylene and using that isobutylene as a raw material.

  As a result, the continuous operation time of the second reaction was 14600 hours, and the continuous operation time until the fourth reaction was 19100 hours.

[Comparative Example 1]
(First reaction)
The first reaction was carried out in the same manner as in Example 1.

(Second reaction)
Subsequent to the first reaction, as shown in FIG. 5, the second reaction was performed in the same manner as in Example 1 except that the temperature of the heat medium bath was changed. The period of continuous operation was 4600 hours. As a result of analyzing the reaction product at this stage, the reaction rate of isobutylene was 95.4%, the selectivity of methacrolein was 88.0%, and the selectivity of methacrylic acid was 5.5%. The temperature of the heat medium bath at this stage is 335 ° C., the average reaction pressure is 100 kPa, and the molecular oxygen / raw material molar ratio in the reaction gas is 2.0 (reaction condition 4).

Claims (3)

  In the presence of a catalyst composed of a complex oxide containing molybdenum, bismuth and iron as essential components, propylene, isobutylene or tertiary butanol as raw materials are vapor-phase catalytically oxidized with molecular oxygen and the corresponding unsaturation A method for producing an aldehyde and an unsaturated carboxylic acid, wherein when the boundary temperature of activation energy of the catalyst is TA ° C, the reaction rate of the raw material is within a temperature range of (TA-15) ° C to TA ° C. A method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, wherein the reaction pressure is controlled so as to be constant.   In the presence of a catalyst composed of a complex oxide containing molybdenum, bismuth and iron as essential components, propylene, isobutylene or tertiary butanol as raw materials are vapor-phase catalytically oxidized with molecular oxygen and the corresponding unsaturation A method for producing an aldehyde and an unsaturated carboxylic acid, wherein when the boundary temperature of activation energy of the catalyst is TA ° C, the reaction rate of the raw material is within a temperature range of (TA-15) ° C to TA ° C. A method for producing an unsaturated aldehyde and an unsaturated carboxylic acid, wherein the control is performed to change the molar ratio of oxygen to the raw material so as to be constant.   The method for producing an unsaturated aldehyde and unsaturated carboxylic acid according to claim 2, wherein the reaction pressure is further changed as the control.

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